The present invention relates to a shift manipulating apparatus for an automatic transmission, and more particularly, to a shift manipulating apparatus for an automatic transmission that can move the spool of a manual valve to identical positions for the range shifts to park or neutral, thereby simplifying the structure of the oil pressure control unit.
In general, a vehicle having an automatic transmission, as shown in FIG. 1, includes a shift lever 10, pivotally installed inside for a driver to select a running mode, and a manual valve 12. Manual valve 12 is a shifting valve that selectively transmits oil pressure to a clutch or brake of the transmission in response to gear changes via movement of the shift lever 10 by the drive. A position control apparatus 14 is installed between the shift lever 10 and manual valve 12 to transmit to the manual valve 12 the shift manipulating force generated by pivot of the shift lever 10. The position control apparatus 14 typically further includes a cable 14a connected with the shift lever 10, an inhibiter switch assembly 14b connected to the cable 14a and pivotally installed at the transmission and a rod 14c connected to the inhibiter switch assembly 14b for transmitting the shift manipulating force to the manual valve 12.
Thus, when the shift lever 10 pivots along a sequence of ranges P-R-N-D-3-2-L when the gear range is shifted, valve spool 12a moves in a straight line at a predetermined rate via the position control apparatus 14. This positions the valve spool relative to the port or ports corresponding to the selected gear range, thereby applying line pressure to a relevant transmission frictional element.
In other words, pivot movement of the shift lever 10 is converted into a straight line movement when passing through the cable 14a of the position control apparatus 14. Then, the straight line movement of the cable 14a is converted into pivot movement again when passing through the inhibitor switch assembly 14b. At last, the pivot movement of the inhibitor switch assembly 14b is converted into a straight line movement again when passing through rod 14c. As a result, a relevant port is opened by movement of valve spool 12a thereby applying line pressure to a relevant frictional element for completion of a shift.
However, there is a problem in the conventional manual valve manipulating apparatus in that there is a difference only in the mechanical operation relative to motion of a parking brake apparatus at ranges P and N, but no difference in the oil pressure control unit of the automatic transmission. In other words, it is necessary to transmit oil pressure to a relevant clutch or brake for ranges R-D-3-2-L of running modes of a vehicle. However, at ranges P and N, where the vehicle is stopped, the manual valve functions to maintain a predetermined level of oil pressure only to lubricate respective elements of a power train and to prevent the oil pressure from being transmitted to clutches or brake. Therefore, it is not meaningful to differentiate ranges P and N in the oil pressure control unit.
Nevertheless, there are problems in the conventional manual valve manipulating apparatus in that the position of the spool 12a is not identical at ranges P and N because the manual valve 12 performs only a simple straight line movement along with pivot movement of the shift lever 10, and that the oil pressure control unit of the valve body is constructed in a complex structure to make identical the switches of an oil path in the two ranges where the spool is differently positioned.
The present invention provides a shift manipulating apparatus for an automatic transmission that can simplify the structure of an oil pressure control unit by modifying the position control apparatus such that the spool of the transmission manual valve is positioned at identical places in ranges P and N.
Preferably the shift manipulating apparatus comprises a shift lever to receive shift range selection manipulating force, a manual valve to control oil pressure in the automatic transmission, and a linkage connecting the shift lever and valve spool to enable the spool to be identically positioned in ranges P and N according to pivot of the shift lever.
According to a further alternative embodiment of the present invention a shift manipulating apparatus is provided for an automatic transmission that includes at least drive, reverse, neutral and park gear ranges (D, R, N and P). The invention thus comprises a gear shift mechanism cooperating with a manual hydraulic valve, wherein the manual valve includes identical hydraulic port positions for both the neutral and park gear ranges. Preferably, the gear shift mechanism comprises a gear shift lever and three linkage members operatively linking the lever to the manual valve. More specifically, a first linkage member has a first end operatively linked to the shift lever, and a second end. A second linkage member has a first end that is operatively linked to the first linkage member second end at a first connection point. The third linkage member has a first end operatively linked to the second linkage member second end at a second connection point and a second end operatively linked to the manual valve. The first connection point is guided to be equally spaced from the manual valve in both the neutral and park gear ranges. In a further preferred embodiment, the first connection point, in the reverse gear range, is guided to a position between the neutral and park gear ranges and spaced closer to the manual valve than in the neutral or park gear ranges.
More preferably, the manual valve comprises a valve body defining the hydraulic ports and a valve spool movable within said body to select ports corresponding to the selected gear range. As such, the third linkage member is linked to the valve spool and the second connection point is guided to move at least substantially parallel to movement of the valve spool. A guide member may be provided having a first channel carrying the first connection point and a second channel carrying the second connection point. The first channel is preferably at least substantially perpendicular to said second channel and includes a raised portion corresponding to the reverse gear range position. The raised portion positions the first connection point closer to the manual valve than when in the park or neutral gear range positions.
In an another embodiment of the invention a manual valve for an automatic transmission is provided. The valve includes a valve body and a valve spool. The valve body defines a plurality of hydraulic ports corresponding to at least drive, reverse, neutral and park gear ranges of the transmission. The valve spool is movable within said body to select between the various hydraulic ports. The valve body is configured such that the valve spool selects the same ports for both the neutral and park gear ranges.